Yes, the direction of the frictional force is opposite the other force, but the latter does not points to the centre of the circle. In fact it is a fictitious force, which arises due to the non-inertial frame of the object in circular motion. (Have you wonder why all motorcyclists bend inwards when they turn?)

Check out centrifugal and centripedal force in wiki or other sources.

However, you can still solve the problem without that part of the knowledge.

In your case, there is only one physical force involved, and that is frictional force. So what do you think supply the centrifugal force needed to maintain circular motion?

It is a banked curve, so not only the force of friction keeps the car on track.
Force involved are gravity, normal force and static friction.

When the speed is greater than the allowed one, the car slides outward and up. When it is less, it slides down and inward.

The car moves along a horizontal circle of radius R so the resultant of all forces is equal to the centripetal force, mv2/R, a horizontal force pointing inward, towards the centre of the circle.
Draw free body diagram and figure out the relation between forces and the banking angle.